Method of preparing bicyclic tetrahydroxylated pyrrolizidines

Abstract

Novel bicyclic tetrahydroxylated pyrrolizidines are disclosed which are inhibitors of glycosidase enzymes. A preferred inhibitor is 1α,2α,6α,7α,7αβ-1,2,6-7-tetrahydroxypyrrolizidine. It is synthesized from D-glycero-D-gulo-heptono-1,4-lactone.

What is claimed is: 
     
       1. A method for the production of 1α,2α,6α,7α,7αβ-1,2,6,7-tetrahydroxypyrrolizidine comprising: (a) reacting D-glycero-D-gulo-heptono-1,4-lactone with a silyl blocking agent to protect the primary hydroxyl group and give a protected lactone,   (b) reacting the protected lactone with 2,2-dimethoxypropane to provide a fully protected lactone,   (c) reacting the fully protected lactone with fluoride ion to cleave at C7 and thereby provide access to nitrogen in the ring and give a primary alcohol,   (d) esterifying the primary alcohol with triflic anhydride to afford a triflate,   (e) reacting the triflate with azide ion to give an azidolactone,   (f) reducing the azidolactone to given an azidodiol,   (g) reacting the azidodiol with methanesulfonyl chloride to provide an azidodimesylate,   (h) catalytically hydrogenating the azidodimesylate in ethanol at ambient temperature,   (i) heating the resulting product in ethanol in the presence of sodium acetate to give a tetracyclic pyrrolizidine, and   (j) removing the acetonide protecting groups of the tetracyclic pyrrolizidine by acid hydrolysis to give 1α,2α,6α,7α,7αβ-1,2,6,7-tetrahydroxypyrrolizidine.